1. Field of the Invention
The invention relates to a dynamic contact surface having a carbon-based coating. The invention further relates to a mechanical system that has a contact surface with a carbon-based coating thereon. The invention still further relates to a process for making the dynamic contact surface.
2. Description of the Prior Art
Some current helicopter designs utilize a cylindrical roller/split angular contact ball bearing combination bearing assembly as the production bearing assemblies for power transmission subsystems, e.g., the main transmission gearbox. The cylindrical rollers, contact ball bearings, the cages, and the inner and outer rings, including the raceways of such bearing assemblies, are typically formed from iron alloys. Iron alloys currently employed include Pyrowear 53, a surface-carburized steel manufactured by Carpenter Technology, and AISI 52100 steel.
A desirable design feature for helicopter power transmission gearboxes is the ability to maintain flight operations for sixty minutes (albeit at reduced power levels sufficient only to sustain level flight operations) under an “oil-out” condition, i.e., if the flow of lubricating/cooling oil to the transmission gearbox is lost. Current production bearing assemblies are not able to provide the foregoing design feature.
One approach to provide the desired design feature for oil-out conditions is to substitute ceramic functional components for the iron alloy functional components in production bearing assemblies to reduce contact friction. Another approach is to employ various coatings to the functional components in production bearing assemblies to reduce contact friction. The latter approach is exemplified in U.S. Pat. No. 5,482,602. Neither of the foregoing approaches provide a reduced level of contact friction sufficient to provide the desired design feature.
It would be further desirable to have a dynamic contact surface having a carbon-based coating exhibiting superior hardness and low frictional resistance. It would be further desirable to have a mechanical system having a contact surface(s) with a carbon-based coating exhibiting superior hardness and low frictional resistance. It would still be further desirable to have a process for depositing such a carbon-based coating on a contact surface. It would yet be further desirable to have a helicopter transmission that is able to function for an extended period of time under oil-out conditions.